Protecting device for electric detonators



Nov. 9, 1926. mamas H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DETONATORS FilGd NOV. 20, 1925 twewlfoz Harry Z. Grmzt Patented Nov. 9, 1926.

UNITED STATES PATENT OFFICE.

HARRY L. GRANT, TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 20, 1925. Serial No. 70,366.

This invention relates to a protecting device for electric detonators of the character of that shown in my copending application, Serial No. 748,214, filed on November 6, 1924.

it Like the device of the application referred to, the protecting device of thepresent invention is intended to be applied to the leadin wires of electric detonators and to serve, while in position, to establish a short circuit between the two lead-in wires, so that any stray currents imposed upon the lead-in wires, outwardly of the point of application of said device, may not find their way to the detonator and prematurely explode the same,

and so that no difference in potential between the lead wires can be created, inwardly ofthe point of application of the device under the influence of accidental or stray currents, under any conditions.

I am aware of the fact that it has been proposed to short circuit the main firing cable leading from the blasting machine. However, that method is of utility only at the time of use. Animportant object of the w present invention is to provide a structure which will be operative with respect to the individual detonators, at all times between the time of manufacture of the detonator and until the same is actually exploded on the job, the structure being of particular utility during the time that the detonator is being transported and while it is being handled about the work preliminary to the act-' ual connection of its lead wires to the main firing cable.

The present application is directed to the protection of a specific form of short circuiting shunt and method of applying the sameot-o the lead-in wires of the individual blasting caps, with its inner endabutting and resting firmly against the terminal end .of the usual insulation of the detonators. In the provision of a structure of this character, which is used only once and then thrown away, it is of importance that it be of a simple and inexpensive nature and one adapted to be applied rapidly by automatic machinery. With this end in view, I have devised the shunt shown in the accompanying drawing wherein:

Fig. 1 is a perspective view of one form of the shunt, before being crimped upon the lead wires of a detonator,

Fig. 2 is aside elevation of a common type ofdetonator with the shunt of Fig. 1 applied thereto,

Fig. 3 is a perspective view of a modified form of shunt before crimping and,

Fig. 4; is an edge view of the shunt of Fig. 3 after crimping.

Like numerals designate corresponding parts in all of the figures of the drawing.

Referring to th drawing, 5 designates the conventional electric detonator and 6 and 7 designate the usual lead-in wires of said detonator.

In the ordinary use of the detonator the flow of current of sufficient strength past an igniting element 8, which connects the inner ends of the wires 6 and 7, explodes the detonator. The lead-in wires are insulated, as indicated at 9 and 10, forsome distance from the detonator and the ends of the lead-in wires are left bare beyond the point where the insulation terminates, to adapt them for ready application to the firing cable, leading from a blasting machine.

In carrying out the present invention, I provide a body 11, preferably of sheet metal. This body constitutes a clip-like shunt and it may be formed of copper, aluminum, lead or any other suitable conductive material. The metal of the clip is pierced, as indicated at 12, to provide an opening for the passage of the lead wires 6 and 7. The clip is bent to the V-form, illustrated in Fig. 1, and after the wires 6 and 7 have been threaded through the opening 12', the clip is crimped forcibly upon the wires. The clip or shunt is preferably so positioned that it abuts the outer end of the insulation upon the wires 6 and 7. It is not to be understood that the device is of utility only when actually touching the ter-.

mination of the insulation. It will give a.

v'ery appreciable measure of protection even and 12 to provide openings for the reception of the bared portions of the wires 6 and 7. After these wires have been threaded through the openings 12 and 12", the metal of the clip or shunt is compressed to flatten the structure and crimp it tightly upon the removed at the time of use of the detonator,

it is stripped longitudinally from the wires 6 and 7. The act of stripping the shunt from the wires, cleans and brightens them and insures a good electrical union between said wires and the firing cable to which they are to be attached. To facilitate the cleaning action-of the shunt as it is stripped from the wires, those portions of the shunt constituting edges which engage said wires, are made as sharp as possible, so that in the stripping action, they will exert a scraping effect upon the lead wires of the detonator.

It is to be understood that the invention is not limited to the precise construction set forth but that it includes within its purview whatever changes fairly come within either the terms or the spirit of the appended claims.

Having described my invention, What- I claim is: 1. The herein described method of applying a short circuiting shunt to the parallel bifilar lead wires of an electric detonator, which consists of threading both of said wires through'an opening formed in a sheet metal plate and then bending said plate upon itself to cause it to firmly grip said wires.

2. The herein described method of applying a shunt to the lead wires of an electric detonator which consists of forming an opening in a piece of sheet metal, bending said metal upon itself across the line of said opening, passing the lead wires through the opening and then exerting pressure upon the metal to grip the wires securely between said bent portions.

3. The herein described method of applying a shunt to the lead wires of an electric detonator, which consists of forming a pair of spaced openings in a sheet metal shunt, bending said metal upon itself across theline of said openings, passing the exposed portions of the wires of the detonator through said openings and then exerting pressure upon the material of the shunt to clamp it firmly upon said wires.

4. A shunt of the character described comprising a sheet metal plate of conductive ma-. terial having an opening formed therethrough and being bent upon itself across the line of said opening.

5. The combination with an electric detonator and its lead wires, portions of which lead Wires are covered by insulating material and portions of which are left bare, of a shunt formed of sheet metal, bent upon itself and. having an opening therethrough at the point of bending and through which the bared portions of the wires of the detonator pass, said shunt lying close to the insulating material upon said wires and being clamped thereon.

6. The combination with an electric detonator and its lead wires, portions of which lead wires are covered by insulating material and portions of which are left bare, of a shunt comprising a piece of metal-having a hole formedtherethrough for the passage of the bared portionsof the wires, said metal being bent into engagement with said bared portions after the passage of the wires through the opening.

In testimony whereof he afiixes his signature.

HARRY L. GRANT. 

